1. Field of the Invention
The present invention relates to a radio-frequency (RF) device and wireless communication device, and more particularly, to an RF device and wireless communication device capable of maintaining radiating efficiency, reducing the design and manufacturing costs as well as being modularized.
2. Description of the Prior Art
A wireless communication device is equipped with an antenna to emit or receive radio waves, so as to exchange radio-frequency (RF) signals and access a wireless communication system. Since radio waves are high-frequency sinusoidal signals, every country in the world standardizes the power of radio waves mainly for preventing from affecting users and/or interfering operations of other wireless communication devices. For example, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) recommends that the value of Specific Absorption Rate (SAR) shall not exceed 2.0 W/Kg, while the Federal Communications Commission (FCC) recommends that the value of SAR shall not exceed 1.6 W/Kg. SAR is a measure of the amount of radio frequency energy absorbed by the living body in a normal electromagnetic radiation environment, and watts per kilogram (W/Kg) is the unit of SAR. Besides, since different communication products are used under different conditions, a distance factor is further taken into consideration when measuring the value of SAR. For example, according to the general regulation, measurement of SAR for a handset wireless communication device such as a mobile device or a smart phone should be taken under a condition that the distance between the handset wireless communication device and a human body is 20 cm.
As well known to those skilled in the art, antenna efficiency is usually affected if attempting to reduce interferences of the wireless communication device itself to the outside environment (i.e. to reduce SAR value of the wireless communication device). Therefore, many methods have been disclosed in the prior art in order to maintain the antenna efficiency. One method is by using a proximity sensor to detect the approach of a human body. That is, the RF power of the wireless communication device is reduced when the proximity sensor detects that a human body is approaching, whereas the RF power of the wireless communication device is kept or moderately increased when the proximity sensor does not detect the approach of any human body. In such a condition, interference can be reduced, and meanwhile, antenna efficiency is kept. In the prior art, the proximity sensor includes a receiver or sensor which contains metal materials to detect capacitance variation, so as to determine whether a human body is approaching. However, the included receiver or sensor affects the antenna efficiency, such that the operating frequency band becomes narrow. In other words, the operating frequency band of the antenna, which is originally suitable for broadband demand, is narrowed due to the added receiver or sensor of the proximity sensor. In such a condition, multiple antennas must be designed separately for various communication systems of nearing frequency band demands, causing increase of design and manufacturing costs, and disadvantage of component managements.
Therefore, the prior art needs to be improved.